CN113462841B - Preparation method of pre-reduced iron ore powder with reduction rate of 30-80% for iron bath smelting reduction ironmaking blowing - Google Patents
Preparation method of pre-reduced iron ore powder with reduction rate of 30-80% for iron bath smelting reduction ironmaking blowing Download PDFInfo
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Abstract
The invention discloses a preparation method of pre-reduced iron ore powder for iron bath smelting reduction ironmaking injection, belongs to the technical field of new ironmaking processes, and solves the problem of low pre-reduction rate of the existing iron bath smelting reduction ironmaking. The preparation method comprises the following steps: step S1, mixing the powdery carbonaceous reducing agent and iron ore powder according to the molar ratio of carbon to oxygen of 0.2-0.7: 1, uniformly mixing to obtain mixed powder particles with the granularity of less than 8mm; and S2, placing the mixed powder particles in a closed steel strip heating furnace for indirect heating reduction, wherein the temperature in the furnace is 900-1100 ℃, and the mixed powder particles stay for 10-100 min in a preheating section and a heating section in the furnace to obtain pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing. The method has the advantages of low per ton iron coal consumption and obvious carbon reduction effect.
Description
Technical Field
The invention relates to the technical field of new iron-making processes, in particular to a preparation method of pre-reduced iron ore powder for iron bath smelting reduction iron-making injection.
Background
Blast furnace iron making is the most important iron making process in the world, but coke and sintered ore are used, and the environmental load of the manufacturing process is large.
The iron bath smelting reduction iron making process is from a Hismelt process in Australia, and is further developed in Shandong Wulong in China, so that the continuous service time of equipment is prolonged. The process directly blows fine ores and pulverized coal with the particle size smaller than 8mm, has obvious advantages in the aspects of sulfur oxide, organic matter emission and the like, but has inherent defects in the field of carbon emission. The one-time coal consumption of ton iron for iron making by iron bath smelting reduction is nearly 1 ton, and is 200-300 kg higher than that of high furnace (containing coking, sintering and pelletizing) iron making.
At present, the iron bath smelting reduction iron making process can adopt a rotary kiln to carry out primary pre-reduction on iron ore powder and then enter a hot material injection system of an iron bath furnace, but the process is difficult to form rings by the rotary kiln, and the like.
Therefore, in order to reduce the carbon emission per ton of iron in the iron bath smelting reduction iron making process, it is necessary to increase the pre-reduction rate of the ore powder, reduce the reduction heat load of the iron bath furnace, and increase the iron bath furnace yield.
Disclosure of Invention
In view of the above analysis, the present invention provides a method for preparing pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing, which can solve at least one of the following technical problems: (1) At present, the pre-reduction rate of iron bath smelting reduction ironmaking is low; and (2) the coal consumption and the cost are high in iron bath smelting reduction ironmaking.
The purpose of the invention is mainly realized by the following technical scheme:
the invention provides a preparation method of pre-reduced iron ore powder for iron bath smelting reduction ironmaking injection, which comprises the following steps:
s1, burdening and uniformly mixing: mixing the powdery carbonaceous reducing agent with iron ore powder according to the molar ratio of carbon to oxygen of 0.2-0.7: 1, uniformly mixing to obtain mixed powder particles with the granularity of less than 8mm;
step S2, heating reduction: and placing the mixed powder particles in a closed steel strip heating furnace for indirect heating reduction, wherein the temperature in the furnace is 900-1100 ℃, and the mixed powder particles stay for 10-100 min in a preheating section and a heating section in the furnace to obtain the pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing.
In a possible design, in the step S2, the reduction ratio of the pre-reduced iron ore powder for iron bath smelting reduction ironmaking injection obtained is 30% to 80%.
In a possible design, in the step S2, the grain size of the pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing obtained is less than 8mm.
In one possible design, in the step S1, iron ore powder with a particle size of 1-8 mm is directly mixed with the powdery carbonaceous reducing agent; iron ore powder with the granularity of less than 1mm is mixed with the powdery carbonaceous reducing agent in advance for granulation, and mixed powder particles with the granularity of 1-8 mm are obtained after granulation.
In one possible design, in step S2, the thickness of the mixed powder is 2-50 mm.
In a possible design, in the step S2, the gas generated in the closed steel strip heating furnace is recovered, and the recovered gas can be used as a heating gas source of the closed steel strip heating furnace.
In a possible design, in step S2, the indirect heater of the closed steel strip heating furnace is a U-shaped heat radiation tube, a W-shaped heat radiation tube, a P-shaped heat radiation tube, or a straight heat radiation tube, and the material of the heat radiation tube is high-temperature heat-resistant steel or nickel-based alloy.
In one possible design, in step S1, caO or Ca (OH) is added during the blending process 2 。
In one possible embodiment, in step S1, the powdered carbonaceous reducing agent is coke powder, coke breeze, anthracite, gas coal, or bituminous coal.
In a possible design, in step S1, the iron ore powder is one or more of iron ore concentrate powder, hematite powder, limonite powder, high phosphate rock powder, red mud, iron oxide red produced by hydrometallurgy, and vanadium-titanium magnetite powder.
The invention can at least realize one of the following beneficial effects:
(1) The method adopts a closed steel strip heating furnace to indirectly heat and reduce, and the carbon-oxygen molar ratio is controlled to be 0.2-0.7: 1, controlling the temperature in the furnace to be 900-1100 ℃, and keeping the mixed powder particles in a preheating section and a heating section in the furnace for 10-100 min to obtain iron powder particles with the reduction rate of 30-80%, so that the comprehensive pre-reduction rate of the pre-reduced iron ore powder can be improved, and the coal powder consumption per ton of iron can be reduced, for example, compared with 950 kg of coal powder consumption per ton of iron for preheating the iron ore powder in a rotary kiln, the coal powder consumption is reduced to about 500 kg, and the carbon reduction effect is obvious.
(2) The method also improves the yield of the prior iron bath reduction, and in the prior rotary kiln prereduction-iron bath reduction process, the reduction rate of the rotary kiln prereduced ore powder is lower than 15 percent in order to realize smooth operation of the process. The reduction rate of the pre-reduced ore powder obtained by the process can reach 30-80%, so that the reduction load and the heat load are reduced for the iron bath reduction process, and the production rate is improved. The pre-reduced ore powder is adopted to replace 25 percent of the rotary kiln to preheat the ore powder, and the molten iron yield of the iron bath reduction process is improved by 15 percent; 50 percent of the molten iron can be replaced, and the yield of the molten iron can be improved by 30 percent. If the pre-reduced ore powder is completely adopted to replace the pre-reduced ore powder of the rotary kiln, the yield of the iron bath reduced molten iron can be improved by more than 60 percent.
(3) In the method, the usage amount of the carbonaceous reducing agent is reduced, so that the sulfur content in the molten iron is reduced to a certain extent, and the subsequent molten iron desulphurization cost is reduced.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings, in which like reference numerals refer to like parts throughout, are for the purpose of illustrating particular embodiments only and are not to be considered limiting of the invention.
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention.
At present, the iron bath smelting reduction iron making process adopts a rotary kiln to preheat iron ore powder (the granularity of the iron ore powder is less than 8 mm), then hot ore powder enters a blowing system (the granularity of raw materials applicable to the blowing system is less than 8 mm), and the hot ore powder is blown into an iron bath furnace by hot spraying to be melted and reduced. As the granularity of the iron ore powder is fine, the temperature in the rotary kiln is higher than 800 ℃, and the ring formation is easy, the temperature in the rotary kiln is controlled to be below 800 ℃ in the production, so the reduction effect of the iron ore powder is very poor, practice shows that the reduction rate of the iron ore powder in the rotary kiln is lower than 15%, the reduction time is long (the retention time reaches 10 hours), the ring formation is easy, the coal consumption is high, 1 ton of sponge iron reaches 1 ton of coal powder, and the method is also an important aspect of high coal consumption of the iron bath smelting reduction iron making process at present. Therefore, a pre-reduction method needs to be developed at present, so that the reduction rate of the fine ore is improved to 30% -80%, the injection requirement of the iron bath smelting reduction furnace is met, and the ton iron coal consumption of the iron bath smelting reduction iron making process is reduced and the yield of the iron bath smelting reduction furnace is improved.
At present, the technology for producing sponge iron or metallic iron powder by reducing iron ore powder is relatively mature, for example, gas-based shaft furnace reduction, reduction by using oxidized pellets or lump ore, reduction by using hydrogen-rich gas reformed by hydrogen or natural gas to obtain metallized pellets with the reduction rate of more than 90%, finmet powdered ore fluidized bed reduction, reduction by using hydrogen-rich gas reformed by hydrogen or natural gas to obtain powdered ore with the reduction rate of less than 8mm in a multi-stage fluidized bed, obtain metallized iron powder with the reduction rate of more than 90%, and then hot-pressing into blocks.
Because pellets and lump ore are used for reduction of the gas-based shaft furnace, the gas-based shaft furnace is incompatible with the injection of an iron bath smelting reduction furnace (the granularity of raw materials suitable for an injection system is less than 8 mm); the Hismelt adopts a fluidized bed for preheating and reduction at the early stage, but the equipment has high failure; and the fluidized bed is changed into a rotary kiln, the reduction rate of the iron ore powder in the rotary kiln is lower than 15%, the reduction time is long (the retention time reaches 10 hours), ring formation is easy, the coal consumption is high, and 1 ton of sponge iron reaches 1 ton of coal powder.
The invention provides a preparation method of pre-reduced iron ore powder for iron bath melting reduction ironmaking blowing, which comprises the following steps:
s1, burdening and uniformly mixing: mixing the powdery carbonaceous reducing agent with iron ore powder according to the molar ratio of carbon to oxygen of 0.2-0.7: 1, uniformly mixing to obtain mixed powder particles with the granularity of less than 8mm;
step S2, heating reduction: and placing the mixed powder particles in a closed steel strip heating furnace for indirect heating reduction, wherein the temperature in the furnace is 900-1100 ℃, and the mixed powder particles stay for 10-100 min in a preheating section and a heating section in the furnace to obtain the pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing.
It should be noted that, the inventors have found through long-term intensive studies that:
for the iron bath smelting reduction iron-making process, if the reduction rate of pre-reduced iron ore powder is too high, the caking property of metal is enhanced, and sticking and blocking are easily caused in the conveying and blowing processes; if the reduction rate of the pre-reduced iron ore powder is too low, the reduction load of the iron bath furnace is large, the coal consumption of the iron bath reduction is high, and the production rhythm is slow. Therefore, in the step S2, the reduction ratio of the obtained pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing is controlled to be 30% to 80%.
Specifically, in order to meet the requirement of the blast of the iron bath smelting reduction furnace, the blast particle size is required, and the particle size of the pre-reduced product to be reduced is less than 8mm, so in the step S2, the particle size of the pre-reduced iron ore powder for blast iron bath smelting reduction iron making is controlled to be less than 8mm.
Specifically, in the step S1, when the particle size difference between the powdered carbonaceous reducing agent and the iron ore powder is large, uneven mixing, insufficient reduction, more residual carbon powder, difficulty in controlling the content of residual carbon, and the like are easily caused in the process of indirect heating reduction in the closed steel strip heating furnace. Therefore, in the step S1, the uniformity of the particle sizes of the powdery carbonaceous reducing agent and the iron ore powder is good.
Specifically, in the step S1, the average particle size of the powdery carbonaceous reducing agent is about 0.15 mm.
Specifically, in the step S1, the iron ore powder with the particle size of 1-8 mm can be directly and uniformly mixed with the powdery carbonaceous reducing agent; for the iron ore powder with the granularity of less than 1mm, the iron ore powder needs to be mixed with the powdery carbonaceous reducing agent in advance for granulation, and mixed powder particles with the granularity of 1-8 mm are obtained after granulation. Preferably, after granulation, a mixed powder particle with a particle size of more than 3mm and less than 8mm is obtained.
Specifically, many granulation devices, such as a roller granulator, a disc granulator, a high-speed rotating granulator, a double-roller ball press, a mixer, etc., can also be used for forming a mixture by stirring through mechanical devices, and the mixture is sieved to obtain mixed powder particles with the particle size of 1-8 mm.
Specifically, in step S1, the powdered carbonaceous reducing agent may be coke powder (dust), anthracite, gas coal, bituminous coal, or the like.
Specifically, in step S1, the molar amount of carbon in the carbon-to-oxygen molar ratio is calculated based on the fixed carbon content in the powdery carbonaceous reducing agent used; the iron ore powder is iron concentrate powder, hematite powder, limonite powder, high phosphorus ore powder, red mud, iron red produced by hydrometallurgy, vanadium-titanium magnetite powder and the like, and the molar weight of oxygen in the iron ore powder is calculated according to the valence proportion of iron in the used iron ore. In the step S1, the molar ratio of carbon to oxygen is controlled to be 0.2 to 0.7, which is based on the finding of the inventors of long-term intensive research.
In order to realize the pre-reduction of the iron ore powder, carbon matching is needed, the carbon matching firstly determines the carbon amount needed by the reduction, and then the carbon matching can be carried out according to the fixed carbon content in the powdery carbonaceous reducing agent. The common iron ore powder is iron ore concentrate powder, hematite powder, limonite powder, high phosphorus ore powder, red mud, iron oxide red produced by hydrometallurgy, vanadium-titanium magnetite powder and the like, the iron valence states of the iron oxide powder, the high phosphorus ore powder, the red mud, the iron oxide red produced by hydrometallurgy, the vanadium-titanium magnetite powder and the like are different, for example, the iron in the magnetite is mainly Fe 3 O 4 The phase of (A) also exists, and a small amount of Fe 2 O 3 Phase, hematite, the iron phase is mainly Fe 2 O 3 Limonite also contains hydroxyl groups. The molar quantity of oxygen of the iron ore is thus calculated from the ratio of the valence states of the iron in the iron ore fines used.
Reduced at low temperatures, the carbon required being less than the stoichiometric ratio for the theoretical reaction, e.g. Fe 2 O 3 And reacting with carbon, wherein the comprehensive reaction formula is as follows:
Fe 2 O 3 +3C＝2Fe+3CO
thus Fe 2 O 3 3mol of carbon is needed for reducing the medium-3 mol of oxygen, and researches show that the Fe is completed at low temperature 2 O 3 The reduction of (2.4-2.7 mol) is actually needed, because the reaction process is also accompanied by partial indirect reduction, and the consumption of carbon is reduced.
In order to obtain the pre-reduction rate of 30-80%, the inventor finds out through long-term and intensive research that: the powdered carbonaceous reducing agent and the iron ore powder are mixed according to the molar ratio of carbon to oxygen which is 20 to 70 percent of the normal and complete reaction. Therefore, in step S1, the carbon-oxygen molar ratio is controlled to be 0.2 to 0.7. Wherein the carbon in the carbon-oxygen molar ratio is calculated according to the fixed carbon content in the used powdery carbonaceous reducing agent; and calculating the molar weight of oxygen in the iron ore powder according to the valence state proportion of iron in the used iron ore.
The pre-reduction reaction rate is closely related to temperature and time, and the higher the temperature is, the faster the reaction is. Higher temperatures correspond to higher reduction rates at the same residence time. Considering that temperatures below 900 c require longer reaction times and temperatures above 1100 c, the material costs of indirect heating can rise dramatically. Therefore, in order to realize the reduction rate of 30-80%, in the step S2, the highest temperature in the furnace is controlled to be 900-1100 ℃, and the residence time of the mixed powder particles in the preheating section and the heating section in the furnace is 10-100 min.
Specifically, in the step S2, the paving thickness of the mixed powder particles is 2-50 mm. Exemplary are, e.g., 2mm,10mm,20mm,25mm,30mm,35mm,40mm,45mm, 50mm.
Specifically, in step S2, in order to reduce dust generated by movement of the material, the closed steel strip heating furnace is adopted, and indirect heating is adopted in the closed steel strip heating furnace; compared with the device adopting internal combustion heating, the device adopting internal combustion heating has large coal consumption required for reaching the same reduction rate due to the weak oxidizing atmosphere of combustion.
Specifically, in step S2, the indirect heating mode may be performed by isolating the heating flame from the material, and heating the sealed container (the transportation steel strip and the material are both located in the sealed container) and arranging the heating members, so that both the upper and lower sides of the transportation steel strip can be heated, rather than simply heating in a single direction. Therefore, the mixed powder particles are placed on the steel belt, the steel belt moves in the furnace to drive materials to enter the preheating zone and the heating zone, and the mode can realize the heating up and down together and improve the heating efficiency.
Specifically, in the step S2, the coal gas generated in the closed steel strip heating furnace can be recycled through the coal gas return and purification system, and the recycled coal gas can be used as a heating gas source of the closed steel strip heating furnace, so that the overall pre-reduction energy consumption is reduced. In order to recover the gas, the sealed steel strip heating furnace needs to ensure the sealing property and the safety of the recovered gas. Specifically, the sealing type steel strip heating furnace can realize the sealing performance through a mechanical structure, water sealing, oil sealing and the like.
Specifically, in the step S2, the indirect heater of the closed steel strip heating furnace is a U-shaped heat radiation tube, a W-shaped heat radiation tube, a P-shaped heat radiation tube, or a straight heat radiation tube, and the material of the heat radiation tube is high-temperature heat-resistant steel or nickel-based alloy; the metal shell can be heated by burning a common burner, and then the metal shell transfers heat to the materials inside.
Specifically, in the step S2, the heating gas source of the closed steel strip heating furnace may be purified gas recovered from the furnace, natural gas, gas produced in the iron bath smelting reduction furnace, or other gas.
Specifically, in step S2, in order to reduce the thermal tensile force caused by the frictional resistance of the steel strip in the furnace in the closed steel strip heating furnace and increase the service temperature of the steel strip, the furnace bottom roller is adopted for transmission, so that the moving speed of the steel strip is consistent with the transmission line speed of the furnace bottom roller, and the transmission resistance of the steel strip in the furnace can be eliminated. Specifically, in order to prolong the service life of the hearth roll, the hearth roll is made of ceramic rolls, high-temperature heat-resistant steel or nickel-based alloy.
Specifically, in step S2, for a production line with a small production capacity, the bottom rollers in the furnace are not needed to reduce the cost of the device, and the steel strip slides on the supporting surface in the heating furnace directly by adopting a dragging mode, namely, by using external driving.
Specifically, in step S2, in order to prevent the deviation of the steel strip and ensure the normal operation of the steel strip, the closed steel strip heating furnace is provided with an automatic deviation rectifying system, and the automatic deviation rectifying system is combined with manual deviation rectifying to prevent the deviation of the steel strip.
Specifically, in the step S2, the reduced hot iron particles can be separated from the steel strip by methods such as closed high-temperature spiral, high-temperature disc discharging, turning and turning of the steel strip on a high-temperature turning roll, and the like, and then enter a hot material injection system of the iron bath furnace.
Specifically, in step S1, caO or Ca (OH) for inhibiting sulfur volatilization can be added during the blending process 2 The concentration of sulfur oxides in the waste flue gas generated in the way is lower than 30mg/m 3 And waste flue gas can be directly discharged. CaO or Ca (OH) 2 The mass of the iron ore powder is 0.5-10% of the mass of the iron ore powder.
Specifically, in step S1, the uniformly mixed powder particles may be dried and then heated and reduced in a closed steel strip heating furnace.
It should be noted that, considering that the production line of the present invention is combined with the iron bath smelting reduction furnace, and the final off-gas of the iron bath smelting reduction furnace needs to be desulfurized, the waste flue gas containing sulfur oxides generated by heating the closed steel strip heating furnace can be intensively treated, so that CaO or Ca (OH) for suppressing sulfur volatilization is not added in the batching process 2 。
Compared with the prior art, the method adopts the indirect heating reduction in the closed steel strip heating furnace, and the carbon-oxygen molar ratio is controlled to be 0.2-0.7: 1, controlling the temperature in the furnace to be 900-1100 ℃, and keeping the mixed powder particles in a preheating section and a heating section in the furnace for 10-100 min to obtain iron powder particles with the reduction rate of 30-80%, so that the comprehensive pre-reduction rate of the pre-reduced iron ore powder can be improved, and the coal powder consumption per ton of iron can be reduced, for example, compared with 950 kg of coal powder consumption per ton of iron for preheating the iron ore powder in a rotary kiln, the coal powder consumption is reduced to about 500 kg (for example, 450-550 kg), and the carbon reduction effect is obvious. Wherein the coal dust consumption per ton of iron refers to the total amount of coal dust consumed for producing 1 ton of iron product.
The method also improves the yield of the prior iron bath reduction, and in the prior rotary kiln prereduction-iron bath reduction process, the reduction rate of the rotary kiln prereduced ore powder is lower than 15 percent in order to realize smooth operation of the process. The reduction rate of the pre-reduced ore powder obtained by the process can reach 30-80%, so that the reduction load and the heat load are reduced for the iron bath reduction process, and the productivity is improved. The pre-reduced ore powder is adopted to replace 25 percent of the rotary kiln to preheat the ore powder, and the molten iron yield of the iron bath reduction process is improved by 15 percent; 50% of the molten iron can be replaced, and the molten iron yield can be improved by 30%. If the pre-reduced ore powder is completely adopted to replace the pre-reduced ore powder of the rotary kiln, the yield of the iron bath reduced molten iron can be improved by more than 60 percent.
In the method, the usage amount of the carbonaceous reducing agent is reduced, so that the sulfur content in the molten iron is reduced to a certain extent, and the subsequent molten iron desulphurization cost is reduced.
Example 1
The embodiment provides a preparation method of pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing, and a process flow chart is shown in figure 1. The specific details are as follows:
the iron ore powder is iron concentrate powder, the components of the iron concentrate powder are shown in Table 1, and the main phase is Fe 3 O 4 The average particle size is 200 mesh. The reducing agent is smokeless powder, the components are shown in table 2, and the average particle size is 100 meshes.
TABLE 1 iron ore concentrate powder Main ingredient/wt%
| T.Fe | SiO 2 | CaO | MgO | Al 2 O 3 |
| 65.3 | 5.6 | 1.2 | 1.2 | 2.3 |
TABLE 2 smokeless powders main ingredient/wt%
| Volatile matter | Ash content | Fixed carbon | Water content | S |
| 8.4 | 9.7 | 77.3 | 3.6 | 0.5 |
The iron ore concentrate powder and the smokeless powder are mixed according to the mass ratio of 100. And then uniformly mixing and granulating in a roller granulator, screening after granulation to obtain mixed powder particles smaller than 8mm, drying the mixed powder particles by a roller until the water content is 5%, wherein a heat source is waste heat smoke from a production system.
The closed steel strip heating furnace adopts a furnace bottom roller transmission mode, the steel strip is made of 310S heat-resistant stainless steel, a W-shaped heat radiation tube is adopted for heating, the heat radiation tube is made of high-temperature nickel-based alloy, the furnace bottom roller is made of quartz, and the positions of the two sides of the steel strip are dynamically adjusted by adopting an online automatic deviation rectifying system. The heating gas source is recovered purified coal gas and natural gas.
And the highest temperature of a heating section in the furnace is 1050 ℃, the materials stay for 30min in the preheating section and the heating section to obtain pre-reduced iron ore powder for injection with the reduction rate of 67%, the pre-reduced iron ore powder for injection is guided into a high-temperature storage bin from a steel belt by adopting a high-temperature disc, and then enters a hot material injection system of the iron bath furnace through a screw.
The coal gas produced in the closed steel belt heating furnace is pumped out by a variable frequency draught fan, and clean coal gas is obtained by cyclone dust removal, water mist dust removal, electric tar removal, indirect cooling and the like. And then returns to the closed steel strip heating furnace as a heat source.
Example 2
The embodiment provides a preparation method of pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing, which comprises the following specific details:
the iron ore powder is hematite powder, the main components of the hematite powder are shown in Table 3, and the main phase is Fe 2 O 3 Less than 8mm. The reducing agent is gas coal, the components are shown in Table 4, and the average particle size is 50 meshes.
TABLE 3 Main component/wt.% of hematite powder
TABLE 4 gas coal main composition/wt.%
| Volatile component | Ash content | Fixed carbon | Water content | S |
| 31.2 | 7.3 | 55.5 | 5.1 | 0.6 |
The hematite powder and the gas coal powder are prepared according to the mass ratio of 100. And then mixed in a blender.
The closed steel strip heating furnace adopts a hearth roller transmission mode, and the steel strip is made of 310S heat-resistant stainless steel. The U-shaped heat radiation pipe is adopted for heating, the heat radiation pipe is made of high-temperature nickel-based alloy, the furnace bottom roller is made of high-temperature heat-resistant steel, and the positions of the two sides of the steel strip are dynamically adjusted by adopting an online automatic deviation rectifying system. The heating gas source is purified coal gas and liquefied petroleum gas.
The highest temperature of a heating section in the furnace is 1000 ℃, the materials stay for 50min in the preheating section and the heating section to obtain pre-reduced iron ore powder for injection with the reduction rate of 36 percent, the pre-reduced iron ore powder for injection is guided into a high-temperature storage bin from a steel belt by adopting high-temperature screws, and then the pre-reduced iron ore powder enters a hot material injection system of the iron bath furnace through the screws.
The coal gas produced in the closed steel belt heating furnace is pumped out by a variable frequency draught fan, and clean coal gas is obtained by cyclone dust removal, water mist dust removal, electric tar removal, indirect cooling, desulfurization and the like. And then returning to the closed steel strip heating furnace for heating.
Example 3
The embodiment provides a preparation method of pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing, which comprises the following specific details:
the iron ore powder is hematite powder, the main components of the hematite powder are shown in Table 3, and the main phase is Fe 2 O 3 The particle size of raw ore powder is less than 8mm, and the raw ore powder is passed throughSieving and crushing to a particle size of less than 1mm. The reducing agent is gas coal, the components are shown in Table 4, and the average particle size is 100 meshes.
The iron ore powder, the coal powder, the slaked lime and the organic binder powder which are smaller than 1mm are prepared according to the mass ratio of 100 to 3, wherein the carbon-oxygen molar ratio is 0.64. Then mixing evenly, preparing 5-8 mm ellipsoids in a ball press, drying in a grate, and heating by waste heat smoke generated by a closed steel strip heating furnace.
The closed steel strip heating furnace adopts a furnace bottom roller transmission mode, a steel strip is made of 310S heat-resistant stainless steel, a U-shaped heat radiation tube is adopted for heating, the material is high-temperature nickel-based alloy, the material of the furnace bottom roller is made of high-temperature heat-resistant steel, and an online automatic deviation rectification system is adopted for dynamically adjusting the positions of the two sides of the steel strip. The heating gas source is the recovered purified gas and coke oven gas.
The highest temperature of a heating section in the furnace is 1080 ℃, the materials stay for 20min in the preheating section and the heating section to obtain pre-reduced iron ore powder for injection with the reduction rate of 73%, the pre-reduced iron ore powder for injection is guided into a high-temperature storage bin from a steel belt by adopting high-temperature screws, and then enters a hot material injection system of the iron bath furnace through the screws.
The coal gas produced by the closed steel strip heating furnace is extracted by a variable frequency draught fan, and then the clean coal gas is obtained through cyclone dust removal, water mist dust removal, electric tar removal, indirect cooling and the like. And then returning to the heating closed steel strip heating furnace.
Example 4
The embodiment provides a preparation method of pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing, which comprises the following specific details:
the iron ore powder is prepared from fine iron oxide powder produced in hydrometallurgy, and the average particle size is less than 20 μm and accounts for 95%. The reducing agent is anthracite, and the average particle size is 150 meshes as shown in Table 2.
TABLE 5 Main component/wt% of fine-grained iron oxide powder
| Fe | Al | Mn | Cr | Mg | C | P | S |
| 60.35 | 0.369 | <0.01 | 1.43 | 0.178 | 0.62 | 0.01 | 0.2 |
The fine iron oxide powder and the anthracite powder are mixed according to the mass ratio of 100 to 17, and the carbon-oxygen molar ratio is 0.68. And then uniformly mixing and granulating in a roller granulator, sieving after granulation to obtain powder particles smaller than 8mm, drying the powder particles by a roller until the moisture content is 3%, and using a heat source to generate waste heat smoke from a production system.
The steel strip used for the closed steel strip heating furnace is made of 310S heat-resistant stainless steel. The steel strip is dragged on a silicon carbide plate by adopting a W-shaped heat radiation tube for heating, the material is high-temperature nickel-based alloy, and the positions of the two sides of the steel strip are dynamically adjusted by adopting an online automatic deviation rectifying system. The heating gas source is recovered purified coal gas and natural gas.
The highest temperature of a heating section in the furnace is 1050 ℃, materials stay for 20min in the preheating section and the heating section to obtain pre-reduced iron ore powder with the reduction rate of 78%, the pre-reduced iron ore powder is separated from a steel belt and led into a high-temperature storage bin by a turning and turning method of the steel belt on a high-temperature turning roller, and then the pre-reduced iron ore powder enters a hot material injection system of the iron bath furnace through a screw.
The coal gas produced by the closed steel strip heating furnace is pumped out by a variable-frequency draught fan, and then is subjected to cyclone dust removal, water mist dust removal, electric tar removal, indirect cooling and the like to obtain clean coal gas. And then returning to the heating closed steel strip heating furnace.
Example 5
The embodiment provides a preparation method of pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing, which comprises the following specific details:
the iron ore powder is prepared from fine iron oxide powder produced in hydrometallurgy, and the average particle size is less than 20 μm and accounts for 95%. The reductant is anthracite, and the average particle size is 150 meshes, shown in Table 2.
The fine-particle iron oxide powder and the coal powder are mixed according to the mass ratio of 100. And then uniformly mixing and granulating in a roller granulator, sieving to obtain mixed powder particles with the particle size of less than 8mm, drying the mixed powder particles by a roller, wherein the water content is 3%, and the heat source is waste heat flue gas from a production system.
The material of the steel strip used for conveying by the closed steel strip heating furnace is 310S heat-resistant stainless steel. The method is characterized in that a 310S heat-resistant stainless steel muffle (the muffle is called an indirect heating interlayer in the domestic powder metallurgy industry and is made of high-temperature-resistant metal materials and is called a metal muffle), a plurality of direct-fired burners heat the muffle, a steel belt slides at the bottom of the muffle, and the positions of two sides of the steel belt are dynamically adjusted by adopting an online automatic deviation correction system. The heating gas source is recovered purified coal gas and natural gas.
The highest temperature of a heating section in the furnace is 920 ℃, materials stay for 70min in the preheating section and the heating section to obtain pre-reduced iron ore powder with the reduction rate of 45%, the pre-reduced iron ore powder is separated from a steel belt and led into a high-temperature storage bin by a turning and turning method of the steel belt on a high-temperature turning roller, and then the pre-reduced iron ore powder enters a hot material injection system of the iron bath furnace through a screw.
The coal gas produced by the closed steel strip heating furnace is extracted by a variable frequency draught fan, and then the clean coal gas is obtained through cyclone dust removal, water mist dust removal, electric tar removal, indirect cooling and the like. And then returning to the heating closed steel strip heating furnace.
Comparative example 1
The comparative example provides a method for preparing pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing, and the specific details are as follows:
the iron ore powder and the reducing agent used in this comparative example were the same as those used in example 1.
(1) The iron ore concentrate powder and the smokeless powder are mixed according to the mass ratio of 100. And then uniformly mixing and granulating in a roller granulator, sieving to obtain mixed powder particles with the particle size of less than 8mm, drying the mixed powder particles by a roller, wherein the water content is 5%, and the heat source is waste heat flue gas from a production system.
The same heating furnace as in example 1 was used, the maximum temperature of the heating section in the furnace was 880 ℃, the material stayed in the preheating section + the heating section for 40min, and pre-reduced iron ore powder for injection with a reduction rate of 25% was obtained, and the pre-reduced iron ore powder for injection was introduced from the steel strip into the high temperature storage bin by high temperature screw, and then entered the hot material injection system of the iron bath furnace by screw.
The heat source of the closed steel strip heating furnace was the same as that of example 1.
In example 1 above, the amount of pulverized coal consumed per ton of iron was 525kg; much lower than 720kg of comparative example 1, and the reduction rate of the pre-reduced iron ore powder for injection of example 1 was high. Therefore, the method has low coal consumption and low carbon emission; the economic benefit is remarkable.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (6)
1. A preparation method of pre-reduced iron ore powder with a reduction rate of 30% -80% for iron bath smelting reduction ironmaking blowing is characterized by comprising the following steps:
s1, burdening and uniformly mixing: mixing the powdery carbonaceous reducing agent with iron ore powder according to the molar ratio of carbon to oxygen of 0.2-0.7: 1, uniformly mixing to obtain mixed powder particles with the granularity of less than 8mm;
step S2, heating reduction: placing the mixed powder particles in a closed steel strip heating furnace for indirect heating reduction, wherein the temperature in the furnace is 900-1100 ℃, and the mixed powder particles stay for 10-100 min in a preheating section and a heating section in the furnace to obtain pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing;
in the step S1, iron ore powder with the granularity of 1-8 mm is directly and uniformly mixed with the powdery carbonaceous reducing agent; mixing iron ore powder with the granularity of less than 1mm with a powdery carbonaceous reducing agent in advance for granulation to obtain mixed powder particles with the granularity of 1-8 mm;
in the step S1, the iron ore powder is one or more of hematite powder, limonite powder, high phosphate rock powder, red mud, iron oxide red produced by hydrometallurgy and vanadium-titanium magnetite powder; in the step S2, the granularity of the pre-reduced iron ore powder for iron bath smelting reduction ironmaking blowing is less than 8mm;
in the step S2, the upper and lower sides of the transport steel strip can be heated by heating the sealed container in an indirect heating manner, instead of simple unidirectional heating.
2. A method as claimed in claim 1, wherein in step S2, the mixed powder particles have a thickness of 2-50 mm.
3. The manufacturing method according to claim 1, wherein in the step S2, the gas generated in the closed steel strip heating furnace is recovered, and the recovered gas can be used as a heating gas source of the closed steel strip heating furnace.
4. The method according to claim 1, wherein in step S2, the indirect heater of the closed steel strip heating furnace is a U-shaped heat radiation tube, a W-shaped heat radiation tube, a P-shaped heat radiation tube, or a straight heat radiation tube, and the heat radiation tube is made of high temperature heat resistant steel or nickel-based alloy.
5. The method according to claim 1, wherein in step S1, caO or Ca (OH) is added during the compounding process 2 。
6. The production method according to any one of claims 1 to 5, wherein in the step S1, the powdery carbonaceous reducing agent is coke powder, coke dust, anthracite, gas coal or bituminous coal.
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